I've used those Magnaflow XL's on 3" exhaust before.. they are NOT quiet. They're just Magnaflow's version of the 3 chambered Flowmaster. They're nice sounding, but very loud, and very Drone-y.
The best performance/quiet muffler you're going to find will be something like a Super Turbo muffler. Dynomax makes a fantastic one that is fairly quiet, as does Thrush and a few other cheaper companies. Ontop of that, adding in a resonator on both ends before or after the mufflers will help.
Though these are just personal experiences.. maybe a muffler/exhaust expert can chime in and help you out.
Good luck! That 3" is always going to be loud!